Method and means for adjusting and assembling lift truck uprights



March 18, 1969 R. F. MCINTOSH METHOD AND MEANS FOR ADJUSTING ANDASSEMBLI LIFT TRUCK UPRIGHTS I of 6 Sheet Filed Aug. 21, 1967 PIC-5. I

ATTORNEY March 18, 1969 MCINTQSH 3,433325 METHOD AND MEANS FOR ADJUSTINGAND ASSEMBLING LIFT TRUCK UPRIGHTS Filed Aug. 21, 1967 Sheet 3 of 6 FIG.3

FIG. 2

INVENTOR RICHARD F. M INTOSH BY MM ATTORNEY March 18, 1969 R. F M INTOSHMETHOD AND MEANS FOR ADJUSTING AND ASSEMBLING LIFT TRUCK UPRIGHTS FiledAug. 21, 1967 Sheet FIG. 4

INVENTOR RICHARD F. M INTOSH 7/ MM ATTORNEY March 18, 1969 R. F. MINTOSH METHOD AND MEANS FOR ADJUSTING AND ASSEMBLI LIFT TRUCK UPRIGHTSFiled Aug. 21, 1967 FIG. 5

INVENTOR RICHARD F. M INTOSH y M ATTORNEY METHOD AND MEANS FOR ADJUSTINGAND A LIFT TRUCK UPRIGHTS Sheet 5 of 6 Filed Aug. 21, 196'? FIG. 8

FIG. 7

ATTORNEY 4 I w R m 0 V 6 2 Q 4 W. M w /m w 6 m f m 9 LI. Jun J it! I ll]4 m M ..c llii kliillfi Q G HHHJY MhW P JWI I HI U I I IH I HH I I HIHHHHIHI I! ll l l l /l V.

RICHARD F. M INTOSH March 18, 1969 R F. MCINTOSH 3,433,325

METHOD AND MEANS FOR ADJUSTING AND ASSEMBLING LIFT TRUCK UPRIGHTS FiledAug. 21, 196'? FIG. 9

Sheet 6 of 6 FIG. IO

CI 1' 1 E T3 I I i ///46 q? a l *l c g u w go 3Q. r80 30 INVENTORRICHARD F. M INTOSH CUM ATTORNEY United States Patent 3,433,325 METHODAND MEANS FOR ADJUSTING AND ASSEMBLING LIFT TRUCK UPRIGHTS Richard F.McIntosh, Battle Creek, Mich., assignor to Clark Equipment Company, acorporation of Michigan Filed Aug. 21, 1967, Ser. No. 662,171

US. Cl. 187-9 15 Claims Int. Cl. B66b 9/20, 7/02 ABSTRACT OF THEDISCLOSURE A lift truck roller mounted extensible mast which includesremovable stop and/or connecting means operably located between outerand inner mast sections. One of the mast sections and the stop orconnecting means are manipulatable and constructed so as to provide animproved structure and method for assembling the mast sections with theguide rollers being mountable thereon subsequent to assembly thereof,and an improved method for adjusting and/or replacing any or all of theguide rollers subsequent to assembly of the mast sections and withoutdisassembling the mast sections one from the other.

Background of the invention The field of art to which the inventionpertains includes elevators, and more specifically portable elevators.

It has long been a problem in the art to which this invention pertainsto construct a roller mounted extensible type mast for lift trucks whichprovides both a sound and safe construction of reasonable cost, and isalso capable of being serviced in a relatively short time with littleinconvenience, particularly as regards ready adjustment or replacementof the guide rollers which support each extensible rail section from thenext outer rail section.

Heretofore it has been common to construct lift truck roller mountedmast such that to adjust or replace the guide rollers on a rail sectionof the mast it has been necessary either to first completely disassemblethe rail sections one from the other thereby necessitating specialequipment such as overhead or truck cranes, or chain falls and the like,or to use relatively expensive threaded or similarly constructedremovable roller shafts to enable the rollers to be adjusted or replacedwithout complete disassembly of the rail sections.

One well-known manner of mounting extensible sections is to mount therollers all on the inner extensible supported section, with no rollersmounted on the next outer rail section. A two-stage mast construction ofthis type is shown, for example, in Johnson Patent 2,321,029 whereinguide rollers are all mounted from the webs of the extensible railsection for supporting it in the outer fixed rnast section. In theJohnson patent only two such guide rollers are mounted from each side ofthe extensible mast section, as well as in exemplary Patent 2,759,562,although in other similar constructions three or more such rollers havebeen mounted from each side of the extensible section at predeterminedvertically spaced intervals. One of the disadvantages of such aconstruction is the necessity of completely disassembling the railsections one from the other in order to adjust or replace the rollers.The above-mentioned patents each utilizes a lower plate member securedacross the bottom of the outer channels of the primary or fixed mastsection in order to prevent the extensible mast section from beinglowered below the outer mast section. Most commonly, rigidifyingcrossbrace members or tie-bars between the respective mast sections areused which overlap in such a manner as to prevent the downward movementof the extensible rail ice sections below the lowermost position of thenext outer section, such as shown in Patent 3,231,047. As also shown inthe latter patent, the aforementioned problem is attempted to bealleviated by an upright construction which involves the use of a longerextensible mast section than the fixed mast section so that theextensible section extends above the upper ends of the stationarysection when fully lowered, guide rollers being mounted from the topedge portion of the fixed section enabling at least the latter guiderollers to be more readily replaced and serviced.

Another solution to the problem is disclosed and claimed in Patent3,213,967 wherein guide rollers are mounted on shafts secured adjacentthe top and bottom of intermediate and inner mast sections,respectively, of a triple-stage upright therein disclosed, with theinner extensible I- beam mast section nested in interlocking relationwith the intermediate I-beam mast section, the respective flanges ofwhich are cut away at the upper front end of the intermediate sectionrails and at the lower rear end of the inner section rails so that therespective rollers are able to bypass one another through the respectiveflange cutouts in assembling and disassembling the mast sections. Thispermits the guide rollers and shafts to 'be preassembled and secured tothe rails while also enabling the use of relatively low cost rollershafts which may be welded to the webs of the rails. However, while thelatter arrangement has proven satisfactory in commercial use, thereremains the disadvantage of having to disassemble the rail sections inorder to replace or adjust the guide rollers. Again, overlappingtie-bars or transverse brace plates between the sides of the mastsections prevent lowering any of the extensible mast sections below thelowermost position of the next outer section.

Summary My invention is capable of a number of different embodiments orforms. Tht basic embodiment disclosed herein comprises a lift truck mastconstruction having an inner telescopic guide roller mounted mastsection and an outer fixed mast section, in which major components suchas the telescopic mast section and the lift cylinder are manipulatablein accordance With one or more methods which allow installation,adjustment and replacement of the guide rollers between the mastsections after the upright is fully assembled and without the need forextraneous equipment, such as a crane or the like, to disassemble themast sections one from another. It is immaterial whether each guideroller shaft is constructed to be removable from the respective webs orare welded in position, although of course, weldments comprise a lowercost means of attachment.

In carrying out my invention I have conceived various methods formanipulating one or more of the upright components involved, all whichmethods result in enabling the inner mast section of a two-stage uprightto be lowered below the outer fixed mast section so as to expose bothupper and lower guide rollers for installation, adjustment orreplacement, as aforesaid, which lowered position is sometimes referredto herein as negative lift. The structure and various methods foraccomplishing this result will appear in detail below.

It is a primary object of the invention to provide methods and means forenabling guide rollers in a certain type of lift truck upright to beserviced with minimum down time and with relative ease, and withoutrequiring disassembly of the upright.

Brief description of the drawing FIGURE 1 is a front view of a lifttruck having mounted thereon a mast which embodies my invention;

FIGURE 2 is an enlarged elevational rear view of the .With the liftcylinder shown in broken lines to illustrate one method of manipulatingthe mast for servicing the guide rollers;

FIGURES 7 and 8 are views similar to FIGS. and 6, but show anothermethod of manipulating the mast; and

FIGURES 9 and 10 are somewhat schematized front elevational views of theupright construction of FIGS. 1-4 with the fork carriage removed,showing exemplary steps of a third method of manipulating the mast forservicing the guide rollers.

Description of the preferred embodiment Referring to FIGS. 14, aconventional industrial lift truck is shown at numeral 10 having a frameand body construction 12 mounted on a pair of steering wheels, notshown, at the rear end thereof and a pair of traction wheels 14forwardly thereof. The truck embodies suitable electric or internalcombustion prime mover means and drive line components for operating thetruck from an operators compartment 16, which includes an operators seatmounted above the engine compartment, operators foot controls, such asaccelerator pedal and brake, not shown, and a plurality of hand controlsand instrumentation some of which can be seen through the uprightincluding a steering wheel 18, a control lever for operating theupright, and a power train control lever 22 on the steering post.

The upright assembly of the present invention is illustrated generallyat numeral 30, it being mounted on the truck by means of a pair ofrearwardly extending support or trunnion plates 32 of the uprightassembly which are adapted to be pivotally mounted by means of openings36 thereof upon bearing portions of the drive axle, not shown, in knownmanner. It comprises in general a fixed mast section 40 which includes apair of transversely spaced opposed channel members 42 of substantiallyC-shaped cross-section, to the rear flanges of which are securedtrunnion plates 32, channel members 42 being arranged to receive aninner mast section 44 formed of two laterally spaced I-beams 46, thelatter section being guide roller supported in mast section 40 andarranged for longitudinal movement relative thereto. A known forkcarriage construction 48 includes generally a pair of fork tines 50supported from a pair of vertically spaced fork bars 52 to which areconnected for elevation in inner mast section 44 :a pair of forkbrackets 54 to each of which is mounted a pair of vertically spacedguide rollers 56 engaging the inner channels of I- beams 46. A bracket58 extends rearwardly of each channel member 42 for connection to therod ends of a pair of upright tilt cylinders, not shown, pivotallyconnected to the truck for tilting the upright forwardly and rearwardlyon its front axle mounting, as is well-known.

Mast section 40 is cross-braced for rigidity at the rear side thereof bymeans of vertically spaced and transversely extending tie-bar members60, 62, 64 and 66, brackets 60 and 62 of which are relatively largeC-shaped members, the flanges of which are notched at 67 to conform tothe rear corner sections of channels 42 and secured, as by welding, tothe web and rear flange portions of said channels, as best shown in FIG.4. Tie-bar or brace member 64 is secured to the rear flanges of channels42 and is shaped to provide a rearwardly extending vertical space whichallows the passage of tiebar members secured to the rear flanges ofI-beams 46,

as will be described. Tie-bar '66 functions mainly as a supportingbracket for a hydraulic piston and cylinder assembly 74 and is securedat its opposite ends to the rear flanges of channels 42, being formedwith forwardly extending and biased strut members 68 and 70 supporting apartial ring 72 centrally of the lower end of the mast in which ismounted cylinder assembly 74.

Piston and cylinder assembly 74 is of a well-known type, such as isshown in above-mentioned Patent 3,213,967. In FIGS. 14 it is shown in acollapsed position, wherein a cross-head 76 is carried at one end of thepiston rod 78 actuatable by a piston head, not shown, in extension andretraction in cylinder 80, which is supported at the bottom end thereofin the socket provided by ring 72. An inlet port, not shown, is adaptedto connect the bottom end of cylinder 80 with a source of pressure fluidon the lift truck. A pair of laterally spaced sheaves or sprockets 82are rotatably mounted on shafts on opposite sides of cross-head 76, onwhich are reeved a pair of lifting chains 84 anchored at their one endsby means of members 86 to an anchor plate 88 secured on cylinder 80, andanchored at the opposite ends to a pair of anchor members 90 secured atthe rear side of lower fork bar 52 by members 92. The upper end ofcylinder assembly 74 is supported on I-beam rails 46 by means of a pairof forwardly biased brackets 94 which are secured to a pair oftransversely spaced rearwardly extending stop blocks 96 which arepreferably cast into cross-head 76. At opposite ends of each bracket 94is mounted a biased roller 98 engaging one of a pair of short verticalangle tracks 100 which are secured to the upper rear flange portions ofinner rails '46 immediately below an upper tie-bar member 102 which issecured to the rear sides of the rear flanges of inner rails 46. Inaddition to tie-bar 102, tie-bars 108 and 110 are secured to the rearflanges of rails 46 in the upper central and lower portions of theupright assembly and adjacent to outer mast tie-bars 62 and 64 when themast is in a collapsed position. The inner mast section is supported bythe outer mast section in its collapsed position, as shown in FIGS. 1-4,by a removable stop block 112 which is adapted to overlap upper outertie-bar 60 and rest in abutment therewith when the mast is collapsed,said stop block being secured to the rear side of inner upper tie-bar102 by four bolt and nut assemblies 114. As may best be seen in FIG. 3,block members 96 underlap tie-bar 102 so that following the firstportion of extension of piston rod 78, during which free-lift" operationof fork carriage 48 occurs, block members 96 then contact the undersideof tie-bar 102 to elevate with cylinder assembly 74 inner mast section44 to a maximum lift position, during which fork carriage 48 travels ata 2:1 movement ratio to the top of extended inner mast section 44. Itwill be noted that the upper or cross-head end of the cylinder assemblyis continuously supported in tracks 100 by roller and bracket assemblies94, 98.

It will be noted that in the particular upright configurationillustrated in the drawings, which is similar to that described indetail in Patent 3,213,967, the inner I-beam 46 are nested in channels42 in such a manner that the forward flanges of the I-beams are disposedforwardly of the forward flanges of the channels, and the rear flangesof said I-beams are disposed within channels 42 and forwardly of therear flanges of the channels. Upper and lower pairs of guide rollers 124and 126, are mounted on corresponding pairs of stub shaft members 130,which may be welded, or otherwise fixedly secured, to the webs of thenested pairs of I-beams and channels, respectively, for supporting theI- beam rails for extension and retraction in channel sections 42.Likewise, the upper and lower pairs of rollers 56, 56 may be mounted onsimilar stub shafts which are secured to fork brackets 54.

Each guide roller and shaft assembly is as shown in detail in FIG. 4A;it comprises a stub shaft 130 having a flanged end 132, the back surface133 of which is preferably welded to the respective web sections of theI- beam and channel section rails, and to the fork brackets 54, asshown. Each roller, as shown, has outer roller portion 134 mounted on aring of ball bearings 136, and an inner race 138 having a sliding fitwith shaft 130 and readily mountable and demountable manually thereon.One or more shims 140 (one is shown in FIG. 4A) are ordinarily mountedon each shaft 130 between flanges 132 and the side of the roller race atthe time of assembly in the upright so that the tightness or clearancein a lateral direction of the upright rails and of the fork carriage maybe readily adjusted. In practice I prefer to use guide rollers which areslightly cocked or canted in opposite directions as described in detailin abovementioned Patent 3,213,967. For the purpose of simplicity,however, they are shown here without such canting, having their axes ofrotation normal to the web of the rail or fork bracket to which eachshaft 130 is secured. In addition to the guide rollers, a pair of sidethrust rollers 142, FIGS. 3 and 4, are connected to the carriage 52 andare adapted to roll along the outer offset edge portion of each innerI-beam member 46, said pair of side thrust rollers cooperating with thelower inner earriage support rollers 56 for preventing a tendency of theupright to spread apart or wedge when the load carriage is eccentricallyloaded, and for resisting side thrust forces imposed upon the loadcarriage.

Cutouts 144 are provided in the upper corner portion of the forwardflange of each channel beam member 42, and in the lower corner portionof the outwardly extending rearward flange of each I-beam member 46(FIG. 4) so that relatively large diameter guide rollers 124 and 126 maybe mounted on shafts 130 within the respective mast sections such thatthe rollers extend through the respective cutout flange portions withattendant advantages as described in said Patent 3,213,967. Cutouts 144are relatively short in length (FIG. 4A) so that the guide rollerscannot bypass one another for assembly and disassembly, as is the casein the construction disclosed in above Patent 3,298,463, for example.Thus, as will be apparent to persons skilled in the art, a tertiarysafety feature is provided which functions to prevent possibleseparation of the upright sections during operation in the event of aloss or shearing off for any reason of internal secondary safety stopmembers 150, which are secured, as by welding, to the rear outer cornerportions of I-beam rails 46 in predetermined vertically spaced relationabove lower rollers 126 and below upper rollers 124. A pair ofadditional safety stop members 152 and 154 are secured in overlappingrelationship to each of fork brackets 54 and opposite side portions oftie-bar 104, respectively, to limit the maximum extension of the forkcarriage in inner mast section 44.

As pointed out above, the internal stops of cylinder assembly 74 will inall ordinary circumstances limit maximum extension of the various mastparts, and the foregoing secondary safety stop members will not, innormal operation, be effective to limit upright extension. However, inthe event that manufacturing specifications for location of certainupright parts are not adhered to, for example, it is possible that theinner mast of the upright and the fork carriage could be extended to anunsafe elevation, which secondary safety stops 150 are located toprevent by abutting upper rollers 124 in the event they should berequired to function to limit mast extension. In the unlikely event thatneither the primary nor secondary stops function for any reason, theaforementioned tertiary safety feature provided by abutment of rollers124 and 126 will prevent disengagement of the inner mast section fromthe outer mast section.

Referring now to FIGS. 5 and 6, I will describe one method ofmanipulating the upright of FIGS. 1-4 to facilitate adjustment orreplacement of rollers 124 and 126. In this embodiment, cross-head 76 iselevated with piston rod 78 to elevate slightly the inner mast section44 by means of block members 96 and tie-bar 102, at which location forkcarriage 48 has been elevated in the inner mast section to the positionshown in FIG. 5 wherein the fork carriage is slightly above itsfree-lift position which is reached when block members 96 first abut thetie-bar 102. Slight elevation of mast section 44 relieves the stressfrom the pair of bolts 114 of supporting the inner mast section on theouter mast section.

With the upright assembly located as in FIG. 5, a securing member, suchas a strap, chain or any other suitable means, may be used to secure thefork carriage to the inner tie-bar 103, for example, or to any othersuitable inner or outer mast member which may be located at a higherelevation than the portion of the carriage to which it is secured. Thisis represented in FIGS. 5 and 6 by a chain 162 which is threaded withminimum slack through the upright around tie-bar 103 and one of the forkbars 52. After thus securing the inner mast section to the fork carriagebolts 114 may be removed, thereby disconnecting stop member 112 fromtie-bar 102, which removes the support of the inner mast section fromthe outermast section, at which point the inner mast section issupported by the cross-head 76. Cross-head 76 may then be lowered belowits normal position of abutment with tie-bar 102, which effects alowering of the inner mast section through its normal collapsed positionto a negative lift position, as shown in FIG. 6. In the latter positionlower rollers 126 and upper rollers 124 become fully exposed.

It will be noted in FIGS. 1, 5 and 6 that the lift truck is shown withthe front wheels 14 located on a pair of short ramp members 160, thepurpose of which is to elevate the upright assembly 30 an additionaldistance above floor level so that with the inner mast section loweredto a negative lift position there is sufiicient space to enable theservicing of lower rollers 126, as will be apparent in viewing FIG. 6.In many upright constructions which are used with hard or cushion tyredlift trucks, there is insufficient vertical space in which to lower theinner upright sufiiciently to completely expose the lower rollers forservicing. Any suitable means can, of course, be used to elevate thefront of the truck for this purpose. Use of ramps 160 is exemplary of asimple means for providing such additional space. The use of largerpneumatic tires on lift trucks normally provides sufficient elevation ofthe upright above floor level to enable roller removal and adjustmentwithout providing additional elevation as by ramps 160; see FIGS. 9 and10 wherein the latter condition is represented.

The guide rollers 124 and 126, each comprising the assembly of FIG. 4A,are preferably manually mounted with a sliding fit on shaft 130, areheld in position during operation of the upright between the webs of therespective mast rails, and are readily adjustable and/or replaceablemanually by adding or subtracting shims 140 as required for uprightlateral tightness, as aforesaid, and by manually sliding off and on eachshaft a new roller, all with the mast sections in the position shown inFIG. 6. Following roller replacement and/ or adjustment, a reversal ofthe above procedure reconditions the upright for normal operation, as inFIGS. l-3. That is, the mast section 44 is raised with carriage 48 fromthe FIG. 6 to the FIG. 5 position, at which bolts 114 are replaced toreconnect stop member 112 to tie-bar 102; chain 162 may then be removed,fork carriage 48 lowered, and the truck driven from ramps 160. It willbe readily appreciated that complete roller servicing can beaccomplished with little time and effort, that no extraneous equipmentis required, such as overhead cranes, and the like, and that, as aconsequence, the procedure can be implemented wherever the lift truckmay be located.

It will also be appreciated that original assembly and adjustment of theupright by the manufacturer is greatly facilitated by this invention.Correct initial lateral adjustment of the mast at the factory is veryimportant since normally the adjustment is not required to be alteredfor a high percentage of the operating life of the mast.

Heretofore, as pointed out in general in the above er1- titledBackground of the Invention, no really adequate solution to the problemhad been devised. By means of my invention, both original factoryassembly of mast sections and adjustment of guide rollers is greatlysimplified in that the mast sections 40 and 44 may be assembled withoutany of guide rollers 124 or 126 mounted on shafts 130. Further, in thenested I-beam construction disclosed, shafts 130 of rollers 124 aredisplaced forwardly of shafts 130 of rollers 126 and, consequently, theymay with facility be welded in position prior to mast section assembly,and be manipulated to readily bypass each other during such assembly.The mast section 44 is telescoped into the mast section 40 duringfactory assembly, preferably with the mast sections in a horizontalposition, to the negative lift position in FIG. '6 in which rollers 124and 126 may be readily mounted by hand and adjusted for predeterminedupright lateral tightness by shims 140. It will be also noted thatduring assembly of the mast sections, stop members 150 are enabled to bewelded in position prior to assembly of the mast sections, and to bypassupper shafts 130 on outer rails 42 during assembly, thus furtherfacilitating the attachment of the various parts in the mast sectionsand the assembly of the mast sections. Cylinder assembly 74 is nextmounted and connected to the various other upright components, andcarriage 48 assembled and connected in the upright. The above proceduregreatly simplifies and hastens factory assembly and adjustment of lifttruck uprights over any procedure known heretofore.

FIGS. 7 and 8 illustrate another embodiment of the invention wherein anoverhead crane mechanism or chain fall, illustrated in the figuresschematically by a pulley and cable assembly 164 and 166, is utilizedfor raising and lowering the inner I-beam section as an alternative tothe use of chain 162 of FIGS. and 6. Thus, cable 166 or equivalentsupport means may be attached to tie-bar 102 laterally outwardly of stopmember 112, the inner I-beam section raised to relieve the stress onstop member 112, and bolts 114 then removed so that mast section 44 canbe lowered by the pulley and cable to the position shown in FIG. 8, inwhich guide rollers 124 and 126 are exposed as in FIG. 6 for adjustmentand/ or replacement. A reversal of the above procedure will, of course,return the upright assembly to its original operating condition. It willbe noted that the foregoing procedure does not necessitate elevation ofthe lift cylinder and fork carriage, although some elevation thereof maybe found desirable to provide additional space for servicing the lowerrollers.

Yet another readily available means for manipulating the upright tocarry out the invention herein employs a simple jack 170 or equivalenthoist device. For purposes of clarification, I have not shown the forkcarriage in the latter figures. It may be found desirable to elevate thecarriage to at least a partial free-lift position, and block the same insaid position so that it cannot interfere with guide roller servicing.On the other hand, in the embodiment of FIGS. 9 and 10 wherein apneumatic tyred truck is blocked by members 160, elevation of the forkcarriage above its normal down position may not be required. In anyevent, jack member 170 may be utilized to elevate inner mast section 44,the same as it is elevated in FIG. 5 by cylinder assembly 74 and in FIG.7 by cable 166, at which elevation stop member 112 is detached, aspreviously, and the inner mast section then lowered by jack 170 to theFIG. 10 position, at which the rollers are serviced, as previously,subsequent to which a reversal of the above procedure will reconditionthe upright assembly for normal operation. In the use of a jack orequivalent device 170, it may be necessary or desirable to use higherramps than ramps 160 with cushion tyred lift trucks, in order to provideadequate room of the jack in manipulating the inner mast section betweenthe negative lift and raised positions shown in the latter figures. Theuse of an overhead chain fall, or jack, may be found particularlydesirable in instances where the lift truck hydraulic system is beingserviced, for example, making temporarily inoperative cylinder assembly74. By use of such extraneous means for manipulating the inner mastsection, the guide rollers can be serviced without necessitatingoperation of the cylinder assembly.

The basic structure and method of my invention can obviously be used inuprights which vary in configuration, the particular uprightrequirements involved dictating the resulting design, including thenumber, location and design of tie-bars, stops, ram support brackets,ram motor elements, and the like. It is intended that all suchvariations and equivalents thereof which fall within the scope of thepresent invention be covered herein. The embodiments of my inventiondescribed in detail above are intended to be exemplary in characteronly, and this disclosure is intended for purposes of illustration andnot as a limitation of the scope of the invention. Numerous variationsand modifications may be made to suit different requirements, and otherchanges, substitutions, additions and omissions may be made in theconstruction and arrangement of the parts, and in the method ofmanipulation of the parts, without necessarily departing from the scopeof the invention.

As a result, it is not my intention to be limited to any particular formof the invention herein illustrated and described except as may appearin the claims appended.

I claim:

1. A mast assembly for lift truck comprising an outer channeled mastmounted from the truck, an inner channeled mast mounted for elevation onthe outer mast, load engaging means mounted for elevation on the innermast, roller means supporting the inner mast on the outer mast includinglower roller means mounted on and adjacent the outer lower end portionof the inner mast and engaging the adjacent channel of the outer mast,and means supporting the inner mast from the outer mast in a verticaldirection when the inner mast is lowered, said latter means beingmanipulated to permit said inner mast to be lowered to a negative liftposition relative to said outer mast, and said lower roller means beingexposed and replaceable when the inner mast is in negative liftposition.

2. A mast assembly as claimed in claim 1 wherein each of said outer andinner masts comprise a pair of vertically extending and transverselyspaced channeled members and a transversely extending brace memberconnecting the side portions of each of said pairs, said manipulatablemeans being secured to an inner mast brace member and normallyoverlapping in a collapsed mast position an adjacent outer mast bracemember which normally prohibits said inner mast to be lowered to saidnegative lift position.

3. A mast assembly as claimed in claim 1 wherein hydraulic motor meansis mounted in said mast assembly for elevating the inner mast relativeto the outer mast, said motor means having a collapsed height less thanthe collapsed height of the mast assembly and adapted to engage saidinner mast for elevation following a predetermined extension of themotor means, said motor means being also adapted to lower said innermast to said negative lift position when said manipulatable means ismanipulated out of supporting relation with said outer mast.

4. A mast assembly as claimed in claim 2 wherein said outer mast bracemember has a generally C-shaped configuration and said inner mast memberis adapted to pass downwardly through the opening of the C-shaped memberwhen said manipulatable means is manipulated out of supporting relationwith said outer mast.

5. A mast assembly as claimed in claim 2 wherein said pair of inner mastmembers includes outwardly extend ing rearward flange portions extendinginto the outer mast channel members, and upper roller means mounted onand adjacent the upper end portions of the outer mast members forengaging said flanges, said upper roller means being also exposed andreplaceable when the inner mast is in said negative lift position.

6. A hoist mechanism for lift trucks comprising a twosection loadlifting frame wherein said sections are in telescoping relation to oneanother, one section having a pair of laterally spaced channeled membersopening inwardly, each member having forward and rearward flangeportions, the second section having a pair of laterally spaced I-shapedmembers nested within the first section such that one end flange of eachI-shaped member is disposed forwardly of the forward leg portion of theadjacent channeled member and the other end flange is disposed inwardlyof the adjacent channeled member, a first roller mounted in the upperend portion of each outer channeled member and a second roller mountedin the bottom end portion of each I-beam member, said rollers supportingsaid second section for telescoping movement on said first section, afirst transverse tie-bar securing said channeled members in fixed spacedrelation and a second transverse tie-bar securing in fixed spacedrelation said I-beam members, said second tie-bar having stop meansconnected thereto for supporting the second frame section verticallyfrom the first frame section when the second section is in downposition, said stop means being movable so as to permit a lowering ofsaid second section below said collapsed position whereby to expose saidfirst and second pairs of rollers.

7. A hoist mechanism as claimed in claim 6 wherein said stop means isdetachable from said second tie-bar, said second tie-bar being movabledownwardly below said first tie-bar when the stop means is detached.

8. A hoist mechanism as claimed in claim 6 wherein lift cylinder meansis mounted for actuating said second section in telescoping relation tosaid first section, said lift motor being shorter in length than thecollapsed height of said load lifting frame for raising and loweringsaid second section to both positive and negative lift positionsrelative to said first section, said roller means being exposed andserviceable when said second section is in said negative lift position.

9. A mast assembly as claimed in claim 1 wherein said roller means aremounted on stub shafts secured as by weldin g to said inner channeledmast members.

10. A method of assembling a lift truck upright having inner and outerchanneled mast means including inner and outer transverse tie-barssecuring opposite sides of the inner and outer mast means, respectively,and roller and roller shaft means supporting the lower portion of theinner mast means in the outer mast means, including the steps oflowering the inner mast means in the outer mast means to a negative liftposition relative to the outer mast means, attaching the roller means tothe roller shaft means on the inner mast means, elevating the inner mastmeans to a positive lift position relative to the outer mast means,connecting vertical support means to the inner mast means so as tooverlap a portion of the outer mast means for supporting the inner mastmeans on the outer mast means, and lowering the inner mast means to anolift position relative to the outer mast means wherein said verticalsupport means abuts the outer mast means.

11. A method of assembling or servicing a lift truck upright as claimedin claim 10 wherein said vertical support means is connected to thetie-bar of the inner mast means in overlapping relation to the tie-barof the outer mast means.

12. A method of servicing the guide rollers of a lift truck uprighthaving an inner mast section mounted for extension and retraction in anouter mast section, the inner mast section having guide roller membersmounted on lower opposite side portions thereof supporting it in theouter mast section, a hydraultic lift motor for raising and lowering theinner mast section in the outer mast section and means supporting theinner mast section directly from the outer mast section in a verticaldirection when the inner mast section is in a no-lift position,comprising the steps of raising the inner mast section so that theoverlapping portion of the vertical support means thereof is above thecooperating support means of the outer mast section, detaching theoverlapping portion of the inner mast support means, lowering the innermast section to a negative lift position relative to the outer mastsection to expose said roller means, servicing said roller means whilein said position, elevating the inner mast means to a positive liftposition, replacing said overlapping vertical support means, andlowering said inner mast means to a no-lift position which is maintainedby said vertical support means.

13. A method as claimed in claim 12 wherein a load lifting carriagemeans is mounted for elevation in the in ner mast comprising theadditional steps of elevating the load carriage partially on the innermast and supporting it in said elevated position during servicing ofsaid guide rollers with the inner mast in a negative lift position.

14. A method as claimed in claim 12 wherein said bydraulic lift motor isof shorter length than the inner mast section is operated to manipulatethe inner mast section to both said positive and negative liftpositions.

15. A method of manipulating a nested d-beam type upright of the typedescribed for servicing upper and lower guide rollers mounted on outerand inner telescoping mast sections respectively, comprising the stepsof elevating the inner mast, manipulating vertical support means of saidinner mast relative to the outer mast thereby conditioning the innermast to be lowered to a negative lift position relative to the outermast, lowering said inner mast to a negative lift position wherein thesaid upper and lower guide rollers are exposed, servicing said upper andlower guide rollers, elevating said inner mast to a positive liftposition relative to the outer mast, and manipulating said vetricalsupport means so as to condition the inner mast for vertical support bythe outer mast.

US. Cl. 18795 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No 3 ,433 ,325 March 18 1969 Richard F. McIntosh It is certifiedthat error appears in the above identified patent and that said LettersPatent are hereby corrected as shown below:

Column 1, line 72, cancel "the", first occurrence. Column 8, line 2,"of" should read for line 44, "manipulated" should read manipulatableline 47, after "in" insert said line 70, after "mast" insert braceSigned and sealed this 14th day of April 1970.

(SEAL) Attest:

Edward M. Fletcher, Jr. E. SCHUYLER, JR.

Attesting Officer Commissioner of Patents

